# CVE-2026-77117: GNU C Library SHIFT_JISX0213 converter hang in iconv

Source: https://junglewise.ai/threats/cve-2026-77117-gnu-c-library-shift-jisx0213-converter-hang-in-iconv  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-15. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-77117 · Severity: medium · CVSS 5.9 · Published 2026-09-15

The GNU C Library's character encoding conversion tool (iconv) contains a flaw in its SHIFT_JISX0213 Japanese character set decoder that can cause applications to hang indefinitely when processing malicious input. An attacker who controls the input data being converted can trigger an infinite loop, denying service to the application and potentially impacting any system that relies on iconv for text encoding conversions.

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

## Quick answers

**Is CVE-2026-77117 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-77117 being exploited in the wild.

**How severe is CVE-2026-77117?** Medium severity, with a CVSS score of 5.9, published 15 September 2026.

**Which products and versions are affected?** Gnu C Library (glibc) 2.3 to 2.44.

**Is there a fix for CVE-2026-77117?** A patch was published on 2026-08-28: Master branch fix released Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-77117 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-77117?** Check whether you run Gnu C Library (glibc) 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.

## Technical details

The vulnerability is a logic error in the SHIFT_JISX0213 decoder within iconvdata/shift_jisx0213.c. When decoding certain SHIFT_JISX0213 sequences that map to two Unicode code points, if the output buffer has insufficient space for the second code point, the converter stores it in state and returns E2BIG. However, the stored pending character is never cleared after emission, causing the converter to repeatedly output the same character without consuming input on subsequent calls. This results in an infinite loop. The attack requires attacker-controlled input and output buffers sized to split the two-code-point sequences. The vulnerability affects glibc versions 2.3 through 2.44; patches are available for versions 2.41 and later.

## Affected products

- GNU C Library (glibc) 2.3 to 2.44

## Timeline

- 2026-08-21: disclosed
- 2026-08-28: patched: Master branch fix released
- 2026-08-29: other: Backports to 2.44, 2.43, 2.42, 2.41 released

## References

- [https://sourceware.org/bugzilla/show_bug.cgi?id=34556](https://sourceware.org/bugzilla/show_bug.cgi?id=34556)
- [https://sourceware.org/git/?p=glibc.git;a=blob_plain;f=advisories/GLIBC-SA-2026-0019](https://sourceware.org/git/?p=glibc.git;a=blob_plain;f=advisories/GLIBC-SA-2026-0019)

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