Memory exhaustion via unbounded LZW stream expansion
Published Oct 22, 2025 · Updated Oct 23, 2025
Denial of service in py-pdf pypdf before 6.1.3 allows attackers to exhaust process memory by parsing a crafted LZWDecode page stream. The LzwCodec.decode method appends expanded chunks to an in-memory BytesIO buffer without limiting cumulative output size. Exploitation requires a consuming application to parse the malicious page content stream; memory exhaustion can hang or terminate that process.
Summary
What happened
Denial of service in py-pdf pypdf before 6.1.3 allows attackers to exhaust process memory by parsing a crafted LZWDecode page stream. The LzwCodec.decode method appends expanded chunks to an in-memory BytesIO buffer without limiting cumulative output size. Exploitation requires a consuming application to parse the malicious page content stream; memory exhaustion can hang or terminate that process.
The record
- CVE
- CVE-2025-62708
- Published
- Oct 22, 2025
- Updated
- Oct 23, 2025
- Vendor
- py-pdf
- Product
- pypdf
- Classifications
- CWE-409, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Oct 22, 2025CVE publishedPublication date reported by the CVE source.
- Oct 23, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 6.1.3
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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