CVE-2026-55586Disclosure

LOWCVSS 6.6 · MEDIUM

Signal is active with 2 mentions in latest observed window

Immediate actions

Track advisory updates for patch or workaround availability

Recommended action window: Monitor and triage in normal cycle

NVD description

SumatraPDF is a multi-format reader for Windows. In 3.6.1 and earlier, a crafted CHM file can supply malformed LZX Huffman code lengths to make_decode_table in ext/CHMLib/lzx.c. In the long-code branch, the function writes new internal nodes through next_symbol before validating that the canonical Huffman table has overflowed. The PRETREE case can write beyond the 104-entry PRETREE_table into adjacent heap state in struct LZXstate when reached through chm_open, chm_retrieve_object, LZXdecompress, and BUILD_TABLE. This produces heap memory corruption in the parser process, while arbitrary code execution has not been demonstrated. No fixed version is available as of this review.

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0.0/ 10 priority

Sources & remediation

Other references

Weakness type (CWE)

CWE-119CWE-787

Priority

LOW

Exploitation

NONE

PoC

NONE

Patch

NONE

Momentum

NONE

Threat summary

2 mentions across 1 observed day

What's happening

Technical details provided in 2 signals
Disclosure: 2 classified signals
2 total mentions across 1 day

Deep dive

Activity timeline2 mentions / 1d

Signal classification1 categories

Disclosure

2100.0%

Referenced assets2 URLs

By indicator

Full discourse2 posts

Infoflowcloud@infoflowcloud47d
Disclosure
🚨*CVE* CVE-2026-55586 SumatraPDF is a multi-format reader for Windows. In 3.6.1 and earlier, a crafted CHM file can supply malformed LZX Huffman code lengths to make_decode_table in ext/CH… https://www.cve.org/CVERecord?id=CVE-2026-55586 ----- Traducción: CVE-2026-55586 Sum… https://infoflow.cloud`
Post summary
The content announces CVE-2026-55586, highlighting a vulnerability in SumatraPDF where malformed CHM files can exploit LZX Huffman code lengths, but it contains no PoC, exploit code, active exploitation, or patch information.
0000028
102 followersView on X
CVE@CVEnew47d
Disclosure
CVE-2026-55586 SumatraPDF is a multi-format reader for Windows. In 3.6.1 and earlier, a crafted CHM file can supply malformed LZX Huffman code lengths to make_decode_table in ext/CH… https://www.cve.org/CVERecord?id=CVE-2026-55586
Post summary
The tweet announces CVE-2026-55586, a vulnerability in SumatraPDF where a crafted CHM file can exploit malformed LZX Huffman code lengths in the decoding routine.
00000784
58.0K followersView on X

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