CVE-2026-29078: Lexbor is a web browser engine library

Q: How do I fix CVE-2026-29078?

lexbor: upgrade to 2.7.0. Exact commands for each OS are on this page.

Q: Is CVE-2026-29078 being exploited?

CVE-2026-29078 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-29078 affect?

CVE-2026-29078 affects lexbor. Severity is high (CVSS 7.5). Lexbor is a web browser engine library. Prior to 2.7.0, the ISO‑2022‑JP encoder in Lexbor fails to reset the temporary size variable between iterations. The statement ctx->buffer_used -= size with a stale size = 3 causes an integer underflo

Routine

HIGH 7.5REMOTEUPGRADE

CVE-2026-29078 is a high-severity flaw (CVSS 7.5) affecting lexbor. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Lexbor is a web browser engine library. Prior to 2.7.0, the ISO‑2022‑JP encoder in Lexbor fails to reset the temporary size variable between iterations. The statement ctx->buffer_used -= size with a stale size = 3 causes an integer underflow that wraps to SIZE_MAX. Afterwards, memcpy is called with a negative length, leading to an out‑of‑bounds read from the stack and an out‑of‑bounds write to the heap. The source data is partially controllable v

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 80%)
CISA exploited list	No
Weakness	CWE-191, CWE-787
Published	2026-03-13
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: lexbor

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-03-13 19:54 UTCPublished CVE record published
2026-06-17 10:29 UTCUpdated Record last modified

lexbor lexbor UPGRADE

Affected: < 2.7.0

Fixed in: 2.7.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy lexbor || rpm -q lexbor || lexbor --version

2. UPGRADE to 2.7.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade lexbor

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade lexbor

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-29078?

lexbor: upgrade to 2.7.0. Exact commands for each OS are on this page.

Is CVE-2026-29078 being exploited?

CVE-2026-29078 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-29078 affect?

CVE-2026-29078 affects lexbor. Severity is high (CVSS 7.5). Lexbor is a web browser engine library. Prior to 2.7.0, the ISO‑2022‑JP encoder in Lexbor fails to reset the temporary size variable between iterations. The statement ctx->buffer_used -= size with a stale size = 3 causes an integer underflo

How urgent is CVE-2026-29078?

Priority 36/100. High severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-29079 HIGH 7.5 UPGRADE Lexbor is a web browser engine library

References

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