CVE-2026-29078
CVE-2026-29078 is a high-severity vulnerability in Lexbor with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-191.
Key facts
- Severity: High (CVSS 3.x base score 7.5)
- CVSS v4: 8.2
- EPSS exploit prediction: 0% (18th percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2026-12051
- Weakness: CWE-191
- Affected product: Lexbor
- Published:
- Last modified:
Description
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 via the contents of the DOM tree. This vulnerability is fixed in 2.7.0.
Frequently asked questions
- What is CVE-2026-29078?
- 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 via the contents of the DOM tree. This vulnerability is fixed in 2.7.0.
- How severe is CVE-2026-29078?
- CVE-2026-29078 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
- Is CVE-2026-29078 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (18th percentile), an estimate of the probability of exploitation in the next 30 days.
- What products are affected by CVE-2026-29078?
- CVE-2026-29078 affects Lexbor. See the affected-products list for the exact vulnerable versions.
- How do I fix CVE-2026-29078?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
- Does CVE-2026-29078 have an EU (EUVD) identifier?
- Yes. CVE-2026-29078 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-12051.
- When was CVE-2026-29078 published?
- CVE-2026-29078 was published on 2026-03-13 and last updated on 2026-06-17.
References
Affected products (1)
- cpe:2.3:a:lexbor:lexbor:*:*:*:*:*:*:*:*
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- CVE-2026-29079 — High (CVSS 7.5): Lexbor is a web browser engine library. Prior to 2.7.0, a type‑confusion vulnerability exists in Lexbor’s HTML…
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