CVE-2026-102997
pypdf: Possible long runtimes for partially malformed FlateDecode streams (Follow-up)
pypdf is a free and open-source pure-python PDF library. Prior to 6.18.1, a crafted PDF containing a partially malformed /FlateDecode stream with padded data can force pypdf/filters.py to use inefficient byte-by-byte decompression while the earlier recovery counter fails to advance for bytes that successfully decode, causing long runtimes and application unavailability. This is a residual issue after the malformed FlateDecode recovery fix. This issue is fixed in version 6.18.1.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
pypdf: Possible long runtimes for partially malformed FlateDecode streams (Follow-up)
pypdf is a free and open-source pure-python PDF library. Prior to 6.18.1, a crafted PDF containing a partially malformed /FlateDecode stream with padded data can force pypdf/filters.py to use inefficient byte-by-byte decompression while the earlier recovery counter fails to advance for bytes that successfully decode, causing long runtimes and application unavailability. This is a residual issue after the malformed FlateDecode recovery fix. This issue is fixed in version 6.18.1.
- Record
CVE-2026-102997- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - Weakness
- CWE-400, CWE-407
- Updated
- 2026-11-02
EUVDEUVD-2026-90373
pypdf is a free and open-source pure-python PDF library. Prior to 6.18.1, a crafted PDF containing a partially malformed /FlateDecode stream with padded data can force pypdf/filters.py to use inefficient byte-by-byte decompression while the earlier recovery counter fails to advance for bytes that successfully decode, causing long runtimes and application unavailability. This is a residual issue after the malformed FlateDecode recovery fix. This issue is fixed in version 6.18.1.
- Record
EUVD-2026-90373- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-jw7q-gvrg-4vj3
pypdf: Possible long runtimes for partially malformed FlateDecode streams (Follow-up)
Impact
An attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires a partially malformed /FlateDecode stream, where the byte-by-byte decompression is used.
Patches
This has been fixed in pypdf==6.18.1.
Workarounds
If you cannot upgrade yet, consider applying the changes from PR #4073.
- Record
GHSA-jw7q-gvrg-4vj3- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - Weakness
- CWE-400, CWE-407
- Updated
- 2026-11-02
NVD
pypdf is a free and open-source pure-python PDF library. Prior to 6.18.1, a crafted PDF containing a partially malformed /FlateDecode stream with padded data can force pypdf/filters.py to use inefficient byte-by-byte decompression while the earlier recovery counter fails to advance for bytes that successfully decode, causing long runtimes and application unavailability. This is a residual issue after the malformed FlateDecode recovery fix. This issue is fixed in version 6.18.1.
- Record
CVE-2026-102997- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/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 - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-400, CWE-407
- Updated
- 2026-11-02
OSV
pypdf: Possible long runtimes for partially malformed FlateDecode streams (Follow-up)
pypdf is a free and open-source pure-python PDF library. Prior to 6.18.1, a crafted PDF containing a partially malformed /FlateDecode stream with padded data can force pypdf/filters.py to use inefficient byte-by-byte decompression while the earlier recovery counter fails to advance for bytes that successfully decode, causing long runtimes and application unavailability. This is a residual issue after the malformed FlateDecode recovery fix. This issue is fixed in version 6.18.1.
- Record
CVE-2026-102997- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - Weakness
- CWE-400, CWE-407
- Updated
- 2026-11-04
OSVDEBIAN-CVE-2026-102997
pypdf is a free and open-source pure-python PDF library. Prior to 6.18.1, a crafted PDF containing a partially malformed /FlateDecode stream with padded data can force pypdf/filters.py to use inefficient byte-by-byte decompression while the earlier recovery counter fails to advance for bytes that successfully decode, causing long runtimes and application unavailability. This is a residual issue after the malformed FlateDecode recovery fix. This issue is fixed in version 6.18.1.
- Record
DEBIAN-CVE-2026-102997- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-03
Show 5 moreShow less
OSVGHSA-jw7q-gvrg-4vj3
pypdf: Possible long runtimes for partially malformed FlateDecode streams (Follow-up)
Impact
An attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires a partially malformed /FlateDecode stream, where the byte-by-byte decompression is used.
Patches
This has been fixed in pypdf==6.18.1.
Workarounds
If you cannot upgrade yet, consider applying the changes from PR #4073.
- Record
GHSA-jw7q-gvrg-4vj3- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - Weakness
- CWE-400, CWE-407
- Updated
- 2026-11-02
OSVPYSEC-2026-4156
pypdf: Possible long runtimes for partially malformed FlateDecode streams (Follow-up)
Impact
An attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires a partially malformed /FlateDecode stream, where the byte-by-byte decompression is used.
Patches
This has been fixed in pypdf==6.18.1.
Workarounds
If you cannot upgrade yet, consider applying the changes from PR #4073.
- Record
PYSEC-2026-4156- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - Updated
- 2026-11-02
OSVUBUNTU-CVE-2026-102997
pypdf is a free and open-source pure-python PDF library. Prior to 6.18.1, a crafted PDF containing a partially malformed /FlateDecode stream with padded data can force pypdf/filters.py to use inefficient byte-by-byte decompression while the earlier recovery counter fails to advance for bytes that successfully decode, causing long runtimes and application unavailability. This is a residual issue after the malformed FlateDecode recovery fix. This issue is fixed in version 6.18.1.
- Record
UBUNTU-CVE-2026-102997- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVCLSA-2026-1791448168 No score
TuxCare security update for pypdf (6 CVEs)
TuxCare rebuilt pypdf to address 6 CVEs. Fixed in 5.9.0.post19+tuxcare.
- Record
CLSA-2026-1791448168- Updated
- 2026-11-02
OSVROOT-APP-PYPI-CVE-2026-102997 No score
CVE-2026-102997 in pypdf - Patched by Root
Root has patched CVE-2026-102997 in the pypdf package for Root:PyPI. Multiple fixed versions available.
- Record
ROOT-APP-PYPI-CVE-2026-102997- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
pypdfPyPI |
before 6.18.1 | 6.18.1 |
pypdfTuxCare:PyPI From an advisory covering 3 CVEs |
5.9.0 up to 5.9.0.post19+tuxcare, plus listed versions 5.9.0.post1+tuxcare5.9.0.post10+tuxcare5.9.0.post11+tuxcare5.9.0.post12+tuxcare5.9.0.post13+tuxcare Show 13 moreShow less5.9.0.post14+tuxcare5.9.0.post15+tuxcare5.9.0.post16+tuxcare5.9.0.post17+tuxcare5.9.0.post18+tuxcare5.9.0.post2+tuxcare5.9.0.post3+tuxcare5.9.0.post4+tuxcare5.9.0.post5+tuxcare5.9.0.post6+tuxcare5.9.0.post7+tuxcare5.9.0.post8+tuxcare5.9.0.post9+tuxcare |
5.9.0.post19+tuxcare |
pypdfDebian:12 |
All versions, plus listed versions 3.17.4-13.4.1-13.4.1-1+deb12u14.0.0-14.0.0-1~exp1 Show 13 moreShow less4.0.1-14.0.2-14.1.0-14.2.0-14.3.1-15.4.0-16.19.0-16.21.0-16.21.1-16.21.4-16.9.0-16.9.2-16.9.2-2 |
None known |
pypdfDebian:13 |
All versions, plus listed versions 5.4.0-16.19.0-16.21.0-16.21.1-16.21.4-16.9.0-16.9.2-16.9.2-2 |
None known |
pypdfDebian:14 |
before 6.19.0-1, plus listed versions 5.4.0-16.9.0-16.9.2-16.9.2-2 |
6.19.0-1 |
pypdf2Debian:12 |
All versions, plus listed versions 2.12.1-32.12.1-3+deb12u12.12.1-4 |
None known |
pypdfPyPI |
before 6.18.1, plus listed versions 1.01.11.101.111.12 Show 45 moreShow less1.131.21.31.41.51.61.71.81.93.1.03.10.03.11.03.11.13.12.03.12.13.12.23.13.03.14.03.15.03.15.13.15.23.15.33.15.43.15.53.16.03.16.13.16.23.16.33.16.43.17.03.17.13.17.23.17.33.17.43.2.03.2.13.3.03.4.03.4.13.5.03.5.13.5.23.6.03.7.03.7.1 |
6.18.1 |
pypdfRoot:PyPI |
before 6.16.1+aikido.1 | 6.16.1+aikido.16.16.2+aikido.26.16.2+aikido.36.16.2+aikido.46.16.2+aikido.56.17.0+aikido.36.18.0+aikido.36.18.0+aikido.46.16.2+aikido.66.16.2+aikido.7 |
pypdf2Ubuntu:Pro:16.04:LTS |
All versions, plus listed versions 1.23+git20141008-11.25.1-11.25.1-1ubuntu0.1~esm11.25.1-1ubuntu0.1~esm2 |
None known |
pypdf2Ubuntu:Pro:18.04:LTS |
All versions, plus listed versions 1.26.0-21.26.0-2ubuntu0.1~esm11.26.0-2ubuntu0.1~esm2 |
None known |
Show 6 moreShow less
| Package | Affected | Fixed |
|---|---|---|
pypdf2Ubuntu:20.04:LTS |
All versions, plus listed versions 1.26.0-21.26.0-3ubuntu11.26.0-3ubuntu1.20.04.11.26.0-3ubuntu1.20.04.2 |
None known |
pypdf2Ubuntu:22.04:LTS |
All versions, plus listed versions 1.26.0-41.26.0-4ubuntu0.22.04.11.26.0-4ubuntu0.22.04.2 |
None known |
pypdfUbuntu:24.04:LTS |
All versions, plus listed versions 3.4.1-13.17.4-14.0.0-14.0.1-14.0.2-1 |
None known |
pypdf2Ubuntu:24.04:LTS |
All versions, plus listed versions 2.12.1-32.12.1-4 |
None known |
pypdfUbuntu:26.10 |
All versions, plus listed versions 6.9.2-16.9.2-2 |
None known |
pypdfUbuntu:26.04:LTS |
All versions, plus listed versions 5.4.0-16.9.2-1 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected | ||
| facts | OSV | |
| affected | OSV | |
| products | NVD | |
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-102997 is a high vulnerability (CVSS 8.7) in Py-pdf Pypdf, published September 30, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.34%, the 27th percentile. Fixed in pypdf 6.18.1.
References
Left out here: 68 versions. The JSON record has them.