VulnerabilityPublished 22 Oct 2026Updated 29 Oct 2026

CVE-2026-112394: Pillow · P;2L and P;4L decoders may read 1 to 3 bytes past the passed buffer size

Affects aiderSource GCVE Database

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Authoritative record:CVE-2026-112394· Medium 6.3

Not known to be exploited · CVSS 6.3 Medium.

Data as of 30 Oct 2026, 07:30 UTC

CVSS 4.0 base score

6.3Medium

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (GitHub_M)	CVSS 4.0	6.3

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: Present
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: Low
Vulnerable system integrity: None
Vulnerable system availability: Low
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: Present: The successful attack depends on the presence of specific deployment and execution conditions of the vulnerable system that enable the attack. These include: a race condition must be won to successfully exploit the vulnerability (the successfulness of the attack is conditioned on execution conditions that are not under full control of the attacker, or the attack may need to be launched multiple times against a single target before being successful); the attacker must inject themselves into the logical network path between the target and the resource requested by the victim (e.g. vulnerabilities requiring an on-path attacker).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the Vulnerable System are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 19 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Homebrewaider`pkg:brew/aider`Other threats	Affected >=0.86.1_1	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

### Summary On `main`, even with the guard in #9725, it's possible to have these decoders read 1 to 3 bytes past the end of the passed buffer with a suitable width/height. ### Details `ImagingRawDecode` and the `P;2L` / `P;4L` unpackers disagree about how many bytes a line of data occupies. The raw decoder derives the line size from the bits per pixel ```c state->bytes = (state->xsize * state->bits + 7) / 8; ``` and uses it both for the bounds check and to advance to the next line. For `P;2L` and `P;4L`, `bits` is 2 and 4 respectively. But these two rawmodes are not packed pixels but 2 or 4 *bit planes*, each padded to a whole number of bytes. `unpackP2L` computes `s = (pixels + 7) / 8` and reads plane *k* at offset `k * s`, and `unpackP4L` does the same across four planes. Their real footprint is therefore `planes * ((xsize + 7) / 8)`. For some widths, padding each plane separately makes this footprint larger than `state->bytes`. For example, at width 1, the decoder accounts for one byte, while the unpackers read two or four bytes. The decoder accepts data that is too short for the last line and on the other hand advances to subsequent lines by less than a line, so every line after the first is also read from the wrong offset. #9725's check is misshapen for this: * It can reject data of the right length: 8x1 `P;2L` image is 2 bytes but is not accepted. * It still accepts buffers shorter than the unpackers require for a given image shape. * It measures the length with `len(data)`, which is an element count rather than a byte count; e.g. `memoryview(array("I", [0,0,0,0,0]))` (20 bytes) is rejected while `mv.tobytes()` is accepted. ### PoC ( `ghsa_p2l_p4l.py`) ```python from array import array from PIL import Image # 1 byte past Image.frombytes("P", (1, 4), array("B", [0] * 4), "raw", "P;2L") # 3 bytes past Image.frombytes("P", (1, 8), array("B", [0] * 8), "raw", "P;4L") ``` is the almost-simplest reproducer. (`array` is needed to get ASan to reliably scream, but the overread is observable with e.g. bytes literals. Python allocates `bytes`es with an extra trailing null byte, from an arena by default to boot, so ASan doesn't see the overread.) On my Mac, I can get ASan to scream about this with ```bash export asan=$(clang -print-file-name=libclang_rt.asan_osx_dynamic.dylib) env CFLAGS="-fsanitize=address -fno-omit-frame-pointer -g -O1" LDFLAGS="-fsanitize=address" uv pip install -e . env DYLD_INSERT_LIBRARIES=$asan PYTHONMALLOC=malloc ASAN_OPTIONS=detect_leaks=0 python3 ghsa_p2l_p4l.py ``` like so: <details> ``` python3(29144,0x202fea2c0) malloc: nano zone abandoned due to inability to reserve vm space. unpackP2L: in=0x602000037370 i=0 j=0 pixels=1 reads 0x602000037370 0x602000037371 unpackP2L: in=0x602000037371 i=0 j=0 pixels=1 reads 0x602000037371 0x602000037372 unpackP2L: in=0x602000037372 i=0 j=0 pixels=1 reads 0x602000037372 0x602000037373 unpackP2L: in=0x602000037373 i=0 j=0 pixels=1 reads 0x602000037373 0x602000037374 ================================================================= ==29144==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000037374 at pc 0x00010778c684 bp 0x00016d029f40 sp 0x00016d029f38 READ of size 1 at 0x602000037374 thread T0 #0 0x00010778c680 in unpackP2L+0x17c (_imaging.cpython-314-darwin.so:arm64+0xb4680) #1 0x000107765360 in ImagingRawDecode+0x348 (_imaging.cpython-314-darwin.so:arm64+0x8d360) #2 0x0001076f259c in _decode+0x15c (_imaging.cpython-314-darwin.so:arm64+0x1a59c) #3 0x0001030d921c in method_vectorcall_VARARGS.llvm.8905850704545875072+0x84 (python3.14:arm64+0x10030521c) #4 0x000102e585b8 in _TAIL_CALL_CALL.llvm.12785051352303791014+0x13c (python3.14:arm64+0x1000845b8) #5 0x000102f1c17c in _PyEval_Vector+0x308 (python3.14:arm64+0x10014817c) #6 0x000102f31864 in PyEval_EvalCode+0x9c (python3.14:arm64+0x10015d864) #7 0x000102f3fa14 in run_mod.llvm.1224844961852478530+0x120 (python3.14:arm64+0x10016ba14) #8 0x000103063eb0 in pyrun_file+0xa0 (python3.14:arm64+0x10028feb0) #9 0x000102dfe834 in _PyRun_SimpleFileObject+0xfc (python3.14:arm64+0x10002a834) #10 0x00010306cb60 in _PyRun_AnyFileObject+0x4c (python3.14:arm64+0x100298b60) #11 0x00010306ca54 in pymain_run_file_obj+0xa0 (python3.14:arm64+0x100298a54) #12 0x000102ffb80c in pymain_run_file+0x44 (python3.14:arm64+0x10022780c) #13 0x000102ff7d0c in Py_RunMain+0x46c (python3.14:arm64+0x100223d0c) #14 0x000102fb0820 in pymain_main.llvm.7308572997346072671+0x1cc (python3.14:arm64+0x1001dc820) #15 0x000102fb0644 in main+0x20 (python3.14:arm64+0x1001dc644) #16 0x000194c86b94 (<unknown module>) 0x602000037374 is located 0 bytes after 4-byte region [0x602000037370,0x602000037374) allocated by thread T0 here: #0 0x0001044a130c in malloc+0x78 (libclang_rt.asan_osx_dynamic.dylib:arm64e+0x3d30c) #1 0x000102f22324 in newarrayobject+0x6c (python3.14:arm64+0x10014e324) #2 0x000102f21b4c in array_new+0x320 (python3.14:arm64

References

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