gh-145376: Fix null pointer deref in md5module.c by eendebakpt · Pull Request #145422 · python/cpython · GitHub

Avoid a null pointer deref in the case of an error path in the constructors (e.g. MD5Type_copy_impl)

Issue found using Claude.

Issue: Various reference leaks in the core #145376

I think this pattern is also present in SHA-* and other modules as it's essentially C/C a b it everywhere.

I think this pattern is also present in SHA-* and other modules as it's essentially C/C a b it everywhere.

Not sure what C/C a b is, but the pattern is indeed the same. E.g.

cpython/Modules/sha1module.c

Line 89 in 02288bf

if (ptr->hash_state != NULL) {

There the hash_state is also set to NULL, not sure why that is.

C/C a b is

it was meant to be a "C/C a bit" and I used C/C for "carbon copy" (which is essentially to mean "copy-paste" for me)

There the hash_state is also set to NULL, not sure why that is.

Likely to prevent a double-free (I don't know if it was me or tiran/gpshead who added this)

Actually it was me in 261633b. I just forgot about the MD5 one I think.

Please add a small NEWS entry.
If you find other issues in MD5, you can include them here as well. Same for SHA-*, BLAKE2 and HMAC.

Oh and please also put the state to NULL just to prevent a possible double-free

Hit the wrong button

…ull_md5module

This one is already part of an other PR actually.

Namely: #145321.

I would prefer merging PR gh-145321 first since it's older and more complete.

Agreed. I am waiting for the other PR and will rebase accordingly.

i just merged the above.

The md5 change LGTM. I'm not sure that it's worth it to add a NEWS entry for this change, since it's unlikely to hit this bug in practice.

I would prefer merging PR gh-145321 first since it's older and more complete.

I prefer to always include a NEWS entry for crashes even if they are rare.

LGTM.

Co-authored-by: Victor Stinner <vstinner@python.org>

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>

@eendebakpt Thanks for the PR! Once it's merged, could you do a manual backport for 3.13 and an automatic backport for 3.14 (though I'm not entirely sure about conflicts in md5module.c)

Thanks @eendebakpt for the PR, and @picnixz for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

…honGH-145422) Fix a possible NULL pointer dereference in `md5module.c` and a double-free in `hmacmodule.c`. Those crashes only occur in error paths taken when the interpreter fails to allocate memory. (cherry picked from commit c1d7768) Co-authored-by: Pieter Eendebak <pieter.eendebak@gmail.com>

GH-145610 is a backport of this pull request to the 3.14 branch.

GH-145611 is a backport of this pull request to the 3.13 branch.

…-145422) (#145610) gh-145376: Fix crashes in `md5module.c` and `hmacmodule.c` (GH-145422) Fix a possible NULL pointer dereference in `md5module.c` and a double-free in `hmacmodule.c`. Those crashes only occur in error paths taken when the interpreter fails to allocate memory. (cherry picked from commit c1d7768) Co-authored-by: Pieter Eendebak <pieter.eendebak@gmail.com>

* gh-145376: Fix crashes in md5module.c Fix a possible NULL pointer dereference in `md5module.c`. This can only occur in error paths taken when the interpreter fails to allocate memory. (cherry-picked from c1d7768) * 📜🤖 Added by blurb_it. * Update Modules/md5module.c --------- Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>

…hon#145422) Fix a possible NULL pointer dereference in `md5module.c` and a double-free in `hmacmodule.c`. Those crashes only occur in error paths taken when the interpreter fails to allocate memory.

eendebakpt added 2 commits March 2, 2026 12:02

Fix null pointer deref in md5module.c

d5b9513

pep7

6cc205c

eendebakpt requested review from gpshead and picnixz as code owners March 2, 2026 14:47

bedevere-app Bot mentioned this pull request Mar 2, 2026

Various reference leaks in the core #145376

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eendebakpt and others added 6 commits March 2, 2026 20:37

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📜🤖 Added by blurb_it.

aae8d22

Merge branch 'null_md5module' of github.com:eendebakpt/cpython into n…

c696867

…ull_md5module

Merge branch 'main' into null_md5module

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Merge branch 'null_md5module' of github.com:eendebakpt/cpython into n…

6b4cbff

…ull_md5module

fix

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Merge branch 'main' into null_md5module

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eendebakpt added 2 commits March 5, 2026 12:53

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Merge branch 'main' into null_md5module

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eendebakpt marked this pull request as ready for review March 5, 2026 12:22

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Merge branch 'main' into null_md5module

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picnixz enabled auto-merge (squash) March 6, 2026 19:38

picnixz merged commit c1d7768 into python:main Mar 6, 2026
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[3.13] gh-145376: Fix crashes in md5module.c (GH-145422) #145611

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eendebakpt deleted the null_md5module branch March 19, 2026 21:39

                           int rc = py_hmac_hinfo_ht_add(table, KEY, value);   \
                           if (rc < 0) {                                       \
-                              PyMem_Free(value);                              \
+                              if (value->refcnt == 0) {                       \

                           int rc = py_hmac_hinfo_ht_add(table, KEY, value);   \
                           if (rc < 0) {                                       \
-                              PyMem_Free(value);                              \
+                              if (value->refcnt == 0) {                       \

gh-145376: Fix null pointer deref in md5module.c by eendebakpt · Pull Request #145422 · python/cpython · GitHub

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gh-145376: Fix null pointer deref in md5module.c - #145422

gh-145376: Fix null pointer deref in md5module.c#145422picnixz merged 14 commits intopython:mainpython/cpython:mainfrom eendebakpt:null_md5moduleeendebakpt/cpython:null_md5moduleCopy head branch name to clipboard

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gh-145376: Fix null pointer deref in md5module.c#145422
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