# CVE-2026-122054: GNU C Library BIG-HKSCS character encoding hang on crafted input

Source: https://junglewise.ai/threats/cve-2026-122054-converting-crafted-big-hkscs-input-to-ucs-4-or-the-internal-wide  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-04. Updated: 2026-11-04  
License: CC BY 4.0 with a link back

CVE-2026-122054 · Severity: medium · CVSS 5.9 · Published 2026-11-04

The GNU C Library's character encoding converter (iconv) can enter an infinite loop when processing specially crafted BIG-HKSCS Chinese text. An attacker controlling the input text and encoding parameters can cause applications using this library to hang indefinitely, leading to denial of service.

Technologies: [Gnu C Library](https://junglewise.ai/threats/technologies/c-library). Vendors: [Gnu](https://junglewise.ai/threats/vendors/gnu).

## Quick answers

**Is CVE-2026-122054 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-122054 being exploited in the wild.

**How severe is CVE-2026-122054?** Medium severity, with a CVSS score of 5.9, published 4 November 2026.

**Which products and versions are affected?** Gnu C Library 2.18 through 2.31.

**Is there a fix for CVE-2026-122054?** Yes: fixed in glibc 2.32. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-122054 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-122054?** Check whether you run Gnu C Library at an affected version. 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.

## How to fix

- Fixed in glibc 2.32

## Technical details

The vulnerability exists in the BIG5-HKSCS gconv converter module where certain double-byte sequences (like 0x88 0x62) map to two Unicode code points. The converter fails to clear its internal state after emitting the second code point, causing subsequent mbrtowc() calls to repeatedly re-emit the saved character without consuming input. This results in an infinite loop when the calling application retries the conversion.

## Affected products

- GNU C Library 2.18 through 2.31

## Timeline

- 2020-03-27: disclosed
- 2026-11-04: patched

## References

- [https://sourceware.org/bugzilla/show_bug.cgi?id=25734](https://sourceware.org/bugzilla/show_bug.cgi?id=25734)
- [https://sourceware.org/git/?p=glibc.git;a=blob_plain;f=advisories/GLIBC-SA-2026-0026](https://sourceware.org/git/?p=glibc.git;a=blob_plain;f=advisories/GLIBC-SA-2026-0026)

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