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`CVE-2026-34478` Apache Log4j

Affected software	Apache Log4j
Severity	6.9 Medium CVSS 4.0 2 scores
Fixed in	`2.25.4`
Weakness	CWE-117
Published	10 Apr 2026
Updated	26 Oct 2026

Description

Apache Log4j Core's Rfc5424Layout https://logging.apache.org/log4j/2.x/manual/layouts.html#RFC5424Layout , in versions 2.21.0 through 2.25.3, is vulnerable to log injection via CRLF sequences due to undocumented renames of security-relevant configuration attributes. Two distinct issues affect users of stream-based syslog services who configure Rfc5424Layout directly: * The newLineEscape attribute was silently renamed, causing newline escaping to stop working for users of TCP framing (RFC 6587), exposing them to CRLF injection in log output. * The useTlsMessageFormat attribute was silently renamed, causing users of TLS framing (RFC 5425) to be silently downgraded to unframed TCP (RFC 6587), without newline escaping. Users of the SyslogAppender are not affected, as its configuration attributes were not modified. Users are advised to upgrade to Apache Log4j Core 2.25.4, which corrects this issue.

CWE-684

Exploitation status

No public exploit

No exploit has been reported in the sources we check.

CISA KEV not listed
VulnCheck KEV not listed
CISA Vulnrichment exploitation: none
Indexed PoC none indexed
EPSS 0.99% chance in 30 days

Waratek protection

No exploit published

Within Waratek scope. In the sources we check, nobody has published exploit code for this CVE or reported it being exploited.

A public code fix exists: apache/logging-log4j2 #4074.

Protection none
Action unverified
Review automated Upstream data
Record active

Decided by

Exploit code for this candidate, published in a reviewed catalogue or a GitHub repository with 5 or more stars, or in use per CISA or VulnCheck; not only a CISA verdict, a forecast, or nothing at all

Finding

This CVE is not listed in CISA KEV or VulnCheck KEV, CISA Vulnrichment records no active exploitation, no reviewed exploit catalogue carries an entry for it, and no GitHub PoC repository for it has 5 or more stars. Nobody has published exploit code worth tracing, so it is not a candidate for a rule ahead of the ones where somebody has; an upstream fix path does exist, so the remediation half of the candidacy still holds. This is a statement about what has been published, not about whether the defect is reachable or serious.

Candidate fix

https://github.com/apache/logging-log4j2/pull/4074 : a pull request: the change under review

CVSS

6.9 MEDIUM v4.0

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

2 metrics

We show the highest score from the newest CVSS version. Scores from different versions can't be compared, and the first score listed is sometimes a 0.0 placeholder.

Version Score Band Vector Assigner Type

CVSS 4.0 6.9 MEDIUM CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X security@apache.org Secondary published

CVSS 3.1 7.5 HIGH CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N NVD Primary

Affected software and releases

Oracle advisories

Advisory

Type

Quarter

Products Oracle names in its risk matrix

Oracle Critical Patch Update October 2026 ↗

CPU

2026-Q4

Oracle Communications / Security (Apache Log4j) (47.0.0.2.0)
Oracle Hospitality Applications / OPERA Login (Apache Log4j) (5.6.28.2)
Oracle Retail Applications / Application Core (Apache Log4j) (15.0, 16.0)
Oracle Retail Applications / Security (Apache Log4j) (19.0.1.044)
Oracle Siebel CRM / Siebel Approval Manager (Apache Log4j) (17.0-26.9)

Oracle Critical Patch Update July 2026 ↗

CPU

2026-Q3

Oracle Communications / Patch Request (Apache Log4j) (8.0.0.7.0-8.3.0.3.0)
Oracle Siebel CRM / EAI (Apache Log4j) (17.0-26.5)
Oracle Siebel CRM / Siebel Approval Manager (Apache Log4j) (17.0-26.5)

Oracle Critical Security Patch Update August 2026 ↗

CSPU

2026-Q3

Oracle Enterprise Manager / EM Plugin: General (Apache Log4j) (13.5.1.0.0-13.5.6.0.0)
Oracle Financial Services Applications / ECM (Apache Log4j) (8.0.8.2, 8.1.2.11)
Oracle Financial Services Applications / Third Party (Apache Log4j) (8.0.8.1, 8.1.2.11)
Oracle Financial Services Applications / User Interface (Apache Log4j) (8.0.8.0)
Oracle Hyperion / Installation/Configuration (Apache Log4j) (11.2.25.0.000)
Oracle Retail Applications / Application Core (Apache Log4j) (15.0, 16.0)
Oracle Retail Applications / NF Issuing (Apache Log4j) (14.2)
Oracle Retail Applications / Operations & Maintenance (Apache Log4j) (15.0, 16.0)
Oracle Supply Chain / CAX Client (Apache Log4j) (3.6)

Oracle Critical Security Patch Update September 2026 ↗

CSPU

2026-Q3

Oracle Communications / Access Service Request (Apache Log4j) (70.0.0)
Oracle Financial Services Applications / Infrastructure (Apache Log4j) (14.5.0.0.0-14.9.0.0.0)

Oracle Critical Security Patch Update June 2026 ↗

CSPU

2026-Q2

Oracle Communications / Other (Apache Log4j) (7.3.6, 7.4.0, 7.5.0, 8.0.0)
Oracle Enterprise Manager / Agent Next Gen (Apache Log4j) (13.5, 24.1)

Oracle components and versions

Family

Component

Versions, as Oracle lists them

Read as

Oracle Communications

Access Service Request (Apache Log4j)

70.0.0

70.0.0

Oracle Communications

Other (Apache Log4j)

7.3.6, 7.4.0, 7.5.0, 8.0.0

7.3.6 · 7.4.0 · 7.5.0 · 8.0.0

Oracle Communications

Patch Request (Apache Log4j)

8.0.0.7.0-8.3.0.3.0

Oracle Communications

Security (Apache Log4j)

47.0.0.2.0

47.0.0.2.0

Oracle Enterprise Manager

Agent Next Gen (Apache Log4j)

13.5, 24.1

13.5 · 24.1

Oracle Enterprise Manager

EM Plugin: General (Apache Log4j)

13.5.1.0.0-13.5.6.0.0

Oracle Financial Services Applications

ECM (Apache Log4j)

8.0.8.2, 8.1.2.11

8.0.8.2 · 8.1.2.11

Oracle Financial Services Applications

Infrastructure (Apache Log4j)

14.5.0.0.0-14.9.0.0.0

Oracle Financial Services Applications

Third Party (Apache Log4j)

8.0.8.1, 8.1.2.11

8.0.8.1 · 8.1.2.11

Oracle Financial Services Applications

User Interface (Apache Log4j)

8.0.8.0

8.0.8.0

Oracle Hospitality Applications

OPERA Login (Apache Log4j)

5.6.28.2

5.6.28.2

Oracle Hyperion

Installation/Configuration (Apache Log4j)

11.2.25.0.000

11.2.25.0.0

Oracle Retail Applications

Application Core (Apache Log4j)

15.0, 16.0

15.0 · 16.0

Oracle Retail Applications

NF Issuing (Apache Log4j)

14.2

14.2

Oracle Retail Applications

Operations & Maintenance (Apache Log4j)

15.0, 16.0

15.0 · 16.0

Oracle Retail Applications

Security (Apache Log4j)

19.0.1.044

19.0.1.44

Oracle Siebel CRM

EAI (Apache Log4j)

17.0-26.5

Oracle Siebel CRM

Siebel Approval Manager (Apache Log4j)

17.0-26.5

Oracle Supply Chain

CAX Client (Apache Log4j)

3.6

3.6

Maven packages

Affected and fixed versions, from OSV.dev

Package Introduced Fixed Last affected

org.apache.logging.log4j:log4j-core 2.21.0 2.25.4 unbounded

org.apache.logging.log4j:log4j-core 3.0.0-beta1 none 3.0.0-beta3

Products and versions

2 products, 6 version entries

Source

Vendor

Product

Scheme

Affected versions

nvd

apache

generic

≥ 2.21.0 and ＜ 2.25.4 · 3.0.0:beta1 · 3.0.0:beta2 · 3.0.0:beta3

osv

org.apache.logging.log4j

generic

≥ 2.21.0 and ＜ 2.25.4 · ≥ 3.0.0 and ≤ 3.0.0

References

URL

Tags

https://github.com/apache/logging-log4j2/pull/4074

pr

https://github.com/apache/logging-log4j2

PACKAGE

https://lists.apache.org/thread/3k1clr2l6vkdnl4cbhjrnt1nyjvb5gwt

WEB

https://logging.apache.org/cyclonedx/vdr.xml

WEB

https://logging.apache.org/log4j/2.x/manual/layouts.html#RFC5424Layout

WEB

https://logging.apache.org/security.html#CVE-2026-34478

WEB

http://www.openwall.com/lists/oss-security/2026/04/10/7

WEB

Timeline

Published

2026-04-10

By the CVE Program.

NVD record modified

2026-10-26

NVD's own last-modified date for this record.

How VRT decided (17 of 24 rules ran)

17 of 24 rules ran. The rest didn't run because an earlier rule had already settled the CVE.

# Rule Outcome Status Detail

identity: Does this identifier describe a vulnerability at all? the first rule that matches decides

1 rejected no match CVE Program withdrawal of this identifier

scope: Is it a vulnerability Waratek protects? the first rule that matches decides

2 armr-patch-file no match An ARMR patch file on disk for this CVE

3 armr-secure-rule-file no match An ARMR security-rule template on disk for this CVE

4 manual-classification no match A researcher's recorded decision for this specific CVE

5 manual classification no match Manual classification of this CVE in the legacy dataset

6 non-java-upstream no match A root cause in non-Java code: an OS kernel, a C library, or a bundled runtime

7 oracle-component no match The defect being in a component of a tracked product the agent does not reach: JavaFX, the Java SE installer, the JInitiator browser plug-in, the native WebLogic proxy plug-in, or a native part of Oracle Application Server or Collaboration Suite (HTTP Server, Web Cache, Internet Directory, mail and calendar servers). Oracle gives these no CPE of their own and names them only in the description.

8 java-client-side no match Oracle's own risk-matrix note saying the CVE is reached only through untrusted code in the Java sandbox (applets, Web Start) or only through a client installation of Java, so a server running its own trusted code is not exposed

9 osv-maven matched In scope Maven packages: org.apache.logging.log4j:log4j-core

10 cna-maven-package not reached An affected Maven artifact named by the CNA itself

11 known-cpe-product not reached An NVD CPE naming a product ARMR tracks

12 cna-cpe-product not reached A CPE the CNA published naming a tracked product. Oracle publishes these on advisory day, months before NVD.

13 oracle-advisory-family not reached A tracked product family named in Oracle's own risk matrix. CPE cannot carry a suite name, only a module.

14 cna-named-product not reached A tracked product named in words by the CVE's own CNA, on a record with no CPE yet. Apache and Eclipse publish these on advisory day, before NVD adds CPE data.

15 non-deployable-product not reached The only affected product being a sealed appliance image, where Java runs but no -javaagent can be attached

16 unmatched-product not reached No tracked product matched above, and none present at all

disposition: What do we do about one that is? every rule runs

17 patch-hint matched Mitigation candidate References include candidate fix URL (pr tier): https://github.com/apache/logging-log4j2/pull/4074

18 open-source-maven skipped The affected package being open source on Maven, so the fix can be read

19 poc-derivable skipped An indexed exploit clearing the evidence bar to reverse-engineer, where there is no source to read

20 no-exploit skipped Nothing to build a rule from yet: no published exploit, no CISA record of exploitation and no source-level change to read

21 secure-rule-match no match A vulnerability class already blocked by an ARMR security rule

22 exploited-no-fix-or-poc skipped Somebody exploiting this CVE (a CISA or VulnCheck KEV listing, or a CISA verdict of active exploitation), with no fix, source code or PoC to build a rule from

23 below-action-threshold withheld CVE ships in Oracle Critical Patch Update October 2026, Oracle Critical Patch Update July 2026, Oracle Critical Security Patch Update August 2026, Oracle Critical Security Patch Update September 2026, Oracle Critical Security Patch Update June 2026 (CPU) — Oracle treats it as urgent, so severity does not settle it

24 no-exploit-published decided it matched No exploit published No exploit code has been published, and an upstream fix path does exist, so the remediation half of the candidacy still holds.

Products the scope rules checked

The products this CVE's record names, and whether VRT tracks each one. The scope rules decided on these.

Vendor Product Tracked CPE Source

apache log4j tracked cpe:2.3:a:apache:log4j:*:*:*:*:*:*:*:* yaml

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