# CVE-2026-89156: PCRE2 out-of-bounds read in pcre2_match after JIT fallback

Source: https://junglewise.ai/threats/cve-2026-89156-pcre2-out-of-bounds-read-in-pcre2-match-after-jit-fallback  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-11. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-89156 · Severity: low · CVSS 2.9 · Published 2026-09-11

PCRE2 is a regular expression matching library used in many applications and systems. When an application processes untrusted input with specific JIT and pattern options, a malformed UTF sequence can cause the library to read beyond the input buffer and crash with a denial-of-service error. This affects any service or application that performs pattern matching on untrusted data.

## Quick answers

**Is CVE-2026-89156 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-89156 being exploited in the wild.

**How severe is CVE-2026-89156?** Low severity, with a CVSS score of 2.9, published 11 September 2026.

**Which products and versions are affected?** PCRE2Project PCRE2 before 10.48.

**Is there a fix for CVE-2026-89156?** A patch was published on 2026-08-31: Fixed in PCRE2 10.48 release Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-89156 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-89156?** Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is an out-of-bounds read in the pcre2_match() function that occurs when JIT compilation is configured for a different matching mode than the one used in the actual match call, causing fallback to the interpreter. The 8-bit PCRE2 library skips UTF validation in the interpreter because JIT already performed a check, but the JIT validation scope is smaller than the interpreter's lookbehind boundary. When processing invalid UTF sequences with unicode word-boundary operations (OP_UCP_WORD_BOUNDARY), unchecked data beyond the subject buffer is read and used as an unbounded index into the Unicode character database, causing a deterministic segmentation fault. Exploitation requires: the application uses pcre2_match() with PCRE2_UTF flag, a non-zero starting offset, a pattern containing lookbehind, and JIT compiled for a different matching mode than used in the call. The fix in PCRE2 10.48 adds a check ensuring JIT supports the requested matching mode before entering JIT validation, otherwise falling back to the interpreter with proper UTF validation.

## Affected products

- PCRE2Project PCRE2 before 10.48

## Timeline

- 2026-08-31: disclosed
- 2026-08-31: patched: Fixed in PCRE2 10.48 release

## References

- [https://github.com/PCRE2Project/pcre2/releases/tag/pcre2-10.48](https://github.com/PCRE2Project/pcre2/releases/tag/pcre2-10.48)
- [https://github.com/PCRE2Project/pcre2/security/advisories/GHSA-2p8c-ff85-vh9x](https://github.com/PCRE2Project/pcre2/security/advisories/GHSA-2p8c-ff85-vh9x)