CVE-2026-27026
published 2026-02-20CVE-2026-27026: pypdf is a free and open-source pure-python PDF library. Prior to 6.7.1, an attacker who uses this vulnerability can craft a PDF which leads to long runtimes…
PriorityP422medium5.5CVSS 3.1
AVLACLPRLUINSUCNINAH
EPSS
0.17%
6.4th percentile
pypdf is a free and open-source pure-python PDF library. Prior to 6.7.1, an attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires a malformed /FlateDecode stream, where the byte-by-byte decompression is used. This vulnerability is fixed in 6.7.1.
Affected
6 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| debian | pypdf | < pypdf 6.9.0-1 (forky) | pypdf 6.9.0-1 (forky) |
| debian | pypdf2 | < pypdf 6.9.0-1 (forky) | pypdf 6.9.0-1 (forky) |
| py-pdf | pypdf | < 6.7.1 | 6.7.1 |
| pypdf_project | pypdf | < 6.7.1 | 6.7.1 |
| pypdf_project | pypdf | >= 0 < 6.9.0-1 | 6.9.0-1 |
| pypdf_project | pypdf | >= 0 < 6.7.1 | 6.7.1 |
CVSS provenance
nvdv3.15.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
nvdv4.06.9MEDIUMCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
osv6.9MEDIUM
vendor_debian6.9MEDIUM
vendor_redhat6.9MEDIUM
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OSV
CVE-2026-27026: pypdf is a free and open-source pure-python PDF library
osv·2026-02-20·CVSS 6.9
CVE-2026-27026 [MEDIUM] CVE-2026-27026: pypdf is a free and open-source pure-python PDF library
pypdf is a free and open-source pure-python PDF library. Prior to 6.7.1, an attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires a malformed /FlateDecode stream, where the byte-by-byte decompression is used. This vulnerability is fixed in 6.7.1.
OSV
pypdf possibly has long runtimes for malformed FlateDecode streams
osv·2026-02-18
CVE-2026-27026 [MEDIUM] pypdf possibly has long runtimes for malformed FlateDecode streams
pypdf possibly has long runtimes for malformed FlateDecode streams
### Impact
An attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires a malformed `/FlateDecode` stream, where the byte-by-byte decompression is used.
### Patches
This has been fixed in [pypdf==6.7.1](https://github.com/py-pdf/pypdf/releases/tag/6.7.1).
### Workarounds
If you cannot upgrade yet, consider applying the changes from PR [#3644](https://github.com/py-pdf/pypdf/pull/3644).
GHSA
pypdf possibly has long runtimes for malformed FlateDecode streams
ghsa·2026-02-18
CVE-2026-27026 [MEDIUM] CWE-770 pypdf possibly has long runtimes for malformed FlateDecode streams
pypdf possibly has long runtimes for malformed FlateDecode streams
### Impact
An attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires a malformed `/FlateDecode` stream, where the byte-by-byte decompression is used.
### Patches
This has been fixed in [pypdf==6.7.1](https://github.com/py-pdf/pypdf/releases/tag/6.7.1).
### Workarounds
If you cannot upgrade yet, consider applying the changes from PR [#3644](https://github.com/py-pdf/pypdf/pull/3644).
Red Hat
pypdf: pypdf: Denial of Service via malformed PDF /FlateDecode stream
vendor_redhat·2026-02-20·CVSS 6.9
CVE-2026-27026 [MEDIUM] CWE-1050 pypdf: pypdf: Denial of Service via malformed PDF /FlateDecode stream
pypdf: pypdf: Denial of Service via malformed PDF /FlateDecode stream
pypdf is a free and open-source pure-python PDF library. Prior to 6.7.1, an attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires a malformed /FlateDecode stream, where the byte-by-byte decompression is used. This vulnerability is fixed in 6.7.1.
A flaw was found in pypdf, a pure-python PDF library. A remote attacker can exploit this vulnerability by crafting a malicious PDF file containing a malformed /FlateDecode stream. This stream, which is used for data compression within the PDF, can cause excessively long processing times when decompressed byte-by-byte. This leads to a Denial of Service (DoS), making the affected system or application unresponsive.
Mitigation: Mitigati
Debian
CVE-2026-27026: pypdf - pypdf is a free and open-source pure-python PDF library. Prior to 6.7.1, an atta...
vendor_debian·2026·CVSS 6.9
CVE-2026-27026 [MEDIUM] CVE-2026-27026: pypdf - pypdf is a free and open-source pure-python PDF library. Prior to 6.7.1, an atta...
pypdf is a free and open-source pure-python PDF library. Prior to 6.7.1, an attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires a malformed /FlateDecode stream, where the byte-by-byte decompression is used. This vulnerability is fixed in 6.7.1.
Scope: local
bookworm: open
forky: resolved (fixed in 6.9.0-1)
sid: resolved (fixed in 6.9.0-1)
trixie: open
No detection rules found.
No public exploits indexed.
2026-02-20
Published