Re: [Buildroot] [PATCH 1/2] package/musl: add upstream security patch for CVE-2026-6042

[Thomas Perale via buildroot <buildroot@buildroot.org>]

In reply of:
> Fixes CVE-2026-6042: musl libc: Algorithmic complexity DoS in iconv
> GB18030 decoder
> https://www.openwall.com/lists/oss-security/2026/04/09/19
> 
> Fixes: https://nvd.nist.gov/vuln/detail/CVE-2026-6042
> 
> Signed-off-by: Fiona Klute <fiona.klute@gmx.de>

Applied to 2025.02.x & 2026.02.x. Thanks

> ---
>  ...-slowness-incorrect-mappings-in-icon.patch | 324 ++++++++++++++++++
>  package/musl/musl.mk                          |   3 +
>  2 files changed, 327 insertions(+)
>  create mode 100644 package/musl/0003-fix-pathological-slowness-incorrect-mappings-in-icon.patch
> 
> diff --git a/package/musl/0003-fix-pathological-slowness-incorrect-mappings-in-icon.patch b/package/musl/0003-fix-pathological-slowness-incorrect-mappings-in-icon.patch
> new file mode 100644
> index 0000000000..5cbc8144d9
> --- /dev/null
> +++ b/package/musl/0003-fix-pathological-slowness-incorrect-mappings-in-icon.patch
> @@ -0,0 +1,324 @@
> +From 67219f0130ec7c876ac0b299046460fad31caabf Mon Sep 17 00:00:00 2001
> +From: Rich Felker <dalias@aerifal.cx>
> +Date: Mon, 30 Mar 2026 16:00:50 -0400
> +Subject: [PATCH] fix pathological slowness & incorrect mappings in iconv
> + gb18030 decoder
> +
> +in order to implement the "UTF" aspect of gb18030 (ability to
> +represent arbitrary unicode characters not present in the 2-byte
> +mapping), we have to apply the index obtained from the encoded 4-byte
> +sequence into the set of unmapped characters. this was done by
> +scanning repeatedly over the table of mapped characters and counting
> +off mapped characters below a running index by which to adjust the
> +running index by on each iteration. this iterative process eventually
> +leaves us with the value of the Nth unmapped character replacing the
> +index, but depending on which particular character that is, the number
> +of iterations needed to find it can be in the tens of thousands, and
> +each iteration traverses the whole 126x190 table in the inner loop.
> +this can lead to run times exceeding an entire second per character on
> +moderate-speed machines.
> +
> +on top of that, the transformation logic produced wrong results for
> +BMP characters above the the surrogate range, as a result of not
> +correctly accounting for it being excluded, and for characters outside
> +the BMP, as a result of a misunderstanding of how gb18030 encodes
> +them.
> +
> +this patch replaces the unmapped character lookup with a single linear
> +search of a list of unmapped ranges. there are only 206 such ranges,
> +and these are permanently assigned and unchangeable as a consequence
> +of the character encoding having to be stable, so a simple array of
> +16-bit start/length values for each range consumes only 824 bytes, a
> +very reasonable size cost here.
> +
> +this new table accounts for the previously-incorrect surrogate
> +handling, and non-BMP characters are handled correctly by a single
> +offset, without the need for any unmapped-range search.
> +
> +there are still a small number of mappings that are incorrect due to
> +late changes made in the definition of gb18030, swapping PUA
> +codepoints with proper Unicode characters. correcting these requires a
> +postprocessing step that will be added later.
> +
> +CVE: CVE-2026-6042
> +Upstream: https://git.musl-libc.org/cgit/musl/commit/?id=67219f0130ec7c876ac0b299046460fad31caabf
> +Signed-off-by: Fiona Klute <fiona.klute@gmx.de>
> +---
> + src/locale/gb18030utf.h | 206 ++++++++++++++++++++++++++++++++++++++++
> + src/locale/iconv.c      |  33 +++++--
> + 2 files changed, 230 insertions(+), 9 deletions(-)
> + create mode 100644 src/locale/gb18030utf.h
> +
> +diff --git a/src/locale/gb18030utf.h b/src/locale/gb18030utf.h
> +new file mode 100644
> +index 00000000..322a2440
> +--- /dev/null
> ++++ b/src/locale/gb18030utf.h
> +@@ -0,0 +1,206 @@
> ++{ 0x80, 36 },
> ++{ 0xa5, 2 },
> ++{ 0xa9, 7 },
> ++{ 0xb2, 5 },
> ++{ 0xb8, 31 },
> ++{ 0xd8, 8 },
> ++{ 0xe2, 6 },
> ++{ 0xeb, 1 },
> ++{ 0xee, 4 },
> ++{ 0xf4, 3 },
> ++{ 0xf8, 1 },
> ++{ 0xfb, 1 },
> ++{ 0xfd, 4 },
> ++{ 0x102, 17 },
> ++{ 0x114, 7 },
> ++{ 0x11c, 15 },
> ++{ 0x12c, 24 },
> ++{ 0x145, 3 },
> ++{ 0x149, 4 },
> ++{ 0x14e, 29 },
> ++{ 0x16c, 98 },
> ++{ 0x1cf, 1 },
> ++{ 0x1d1, 1 },
> ++{ 0x1d3, 1 },
> ++{ 0x1d5, 1 },
> ++{ 0x1d7, 1 },
> ++{ 0x1d9, 1 },
> ++{ 0x1db, 1 },
> ++{ 0x1dd, 28 },
> ++{ 0x1fa, 87 },
> ++{ 0x252, 15 },
> ++{ 0x262, 101 },
> ++{ 0x2c8, 1 },
> ++{ 0x2cc, 13 },
> ++{ 0x2da, 183 },
> ++{ 0x3a2, 1 },
> ++{ 0x3aa, 7 },
> ++{ 0x3c2, 1 },
> ++{ 0x3ca, 55 },
> ++{ 0x402, 14 },
> ++{ 0x450, 1 },
> ++{ 0x452, 7102 },
> ++{ 0x2011, 2 },
> ++{ 0x2017, 1 },
> ++{ 0x201a, 2 },
> ++{ 0x201e, 7 },
> ++{ 0x2027, 9 },
> ++{ 0x2031, 1 },
> ++{ 0x2034, 1 },
> ++{ 0x2036, 5 },
> ++{ 0x203c, 112 },
> ++{ 0x20ad, 86 },
> ++{ 0x2104, 1 },
> ++{ 0x2106, 3 },
> ++{ 0x210a, 12 },
> ++{ 0x2117, 10 },
> ++{ 0x2122, 62 },
> ++{ 0x216c, 4 },
> ++{ 0x217a, 22 },
> ++{ 0x2194, 2 },
> ++{ 0x219a, 110 },
> ++{ 0x2209, 6 },
> ++{ 0x2210, 1 },
> ++{ 0x2212, 3 },
> ++{ 0x2216, 4 },
> ++{ 0x221b, 2 },
> ++{ 0x2221, 2 },
> ++{ 0x2224, 1 },
> ++{ 0x2226, 1 },
> ++{ 0x222c, 2 },
> ++{ 0x222f, 5 },
> ++{ 0x2238, 5 },
> ++{ 0x223e, 10 },
> ++{ 0x2249, 3 },
> ++{ 0x224d, 5 },
> ++{ 0x2253, 13 },
> ++{ 0x2262, 2 },
> ++{ 0x2268, 6 },
> ++{ 0x2270, 37 },
> ++{ 0x2296, 3 },
> ++{ 0x229a, 11 },
> ++{ 0x22a6, 25 },
> ++{ 0x22c0, 82 },
> ++{ 0x2313, 333 },
> ++{ 0x246a, 10 },
> ++{ 0x249c, 100 },
> ++{ 0x254c, 4 },
> ++{ 0x2574, 13 },
> ++{ 0x2590, 3 },
> ++{ 0x2596, 10 },
> ++{ 0x25a2, 16 },
> ++{ 0x25b4, 8 },
> ++{ 0x25be, 8 },
> ++{ 0x25c8, 3 },
> ++{ 0x25cc, 2 },
> ++{ 0x25d0, 18 },
> ++{ 0x25e6, 31 },
> ++{ 0x2607, 2 },
> ++{ 0x260a, 54 },
> ++{ 0x2641, 1 },
> ++{ 0x2643, 2110 },
> ++{ 0x2e82, 2 },
> ++{ 0x2e85, 3 },
> ++{ 0x2e89, 2 },
> ++{ 0x2e8d, 10 },
> ++{ 0x2e98, 15 },
> ++{ 0x2ea8, 2 },
> ++{ 0x2eab, 3 },
> ++{ 0x2eaf, 4 },
> ++{ 0x2eb4, 2 },
> ++{ 0x2eb8, 3 },
> ++{ 0x2ebc, 14 },
> ++{ 0x2ecb, 293 },
> ++{ 0x2ffc, 4 },
> ++{ 0x3004, 1 },
> ++{ 0x3018, 5 },
> ++{ 0x301f, 2 },
> ++{ 0x302a, 20 },
> ++{ 0x303f, 2 },
> ++{ 0x3094, 7 },
> ++{ 0x309f, 2 },
> ++{ 0x30f7, 5 },
> ++{ 0x30ff, 6 },
> ++{ 0x312a, 246 },
> ++{ 0x322a, 7 },
> ++{ 0x3232, 113 },
> ++{ 0x32a4, 234 },
> ++{ 0x3390, 12 },
> ++{ 0x339f, 2 },
> ++{ 0x33a2, 34 },
> ++{ 0x33c5, 9 },
> ++{ 0x33cf, 2 },
> ++{ 0x33d3, 2 },
> ++{ 0x33d6, 113 },
> ++{ 0x3448, 43 },
> ++{ 0x3474, 298 },
> ++{ 0x359f, 111 },
> ++{ 0x360f, 11 },
> ++{ 0x361b, 765 },
> ++{ 0x3919, 85 },
> ++{ 0x396f, 96 },
> ++{ 0x39d1, 14 },
> ++{ 0x39e0, 147 },
> ++{ 0x3a74, 218 },
> ++{ 0x3b4f, 287 },
> ++{ 0x3c6f, 113 },
> ++{ 0x3ce1, 885 },
> ++{ 0x4057, 264 },
> ++{ 0x4160, 471 },
> ++{ 0x4338, 116 },
> ++{ 0x43ad, 4 },
> ++{ 0x43b2, 43 },
> ++{ 0x43de, 248 },
> ++{ 0x44d7, 373 },
> ++{ 0x464d, 20 },
> ++{ 0x4662, 193 },
> ++{ 0x4724, 5 },
> ++{ 0x472a, 82 },
> ++{ 0x477d, 16 },
> ++{ 0x478e, 441 },
> ++{ 0x4948, 50 },
> ++{ 0x497b, 2 },
> ++{ 0x497e, 4 },
> ++{ 0x4984, 1 },
> ++{ 0x4987, 20 },
> ++{ 0x499c, 3 },
> ++{ 0x49a0, 22 },
> ++{ 0x49b8, 703 },
> ++{ 0x4c78, 39 },
> ++{ 0x4ca4, 111 },
> ++{ 0x4d1a, 148 },
> ++{ 0x4daf, 81 },
> ++{ 0x9fa6, 14426 },
> ++{ 0xe76c, 1 },
> ++{ 0xe7c8, 1 },
> ++{ 0xe7e7, 13 },
> ++{ 0xe815, 1 },
> ++{ 0xe819, 5 },
> ++{ 0xe81f, 7 },
> ++{ 0xe827, 4 },
> ++{ 0xe82d, 4 },
> ++{ 0xe833, 8 },
> ++{ 0xe83c, 7 },
> ++{ 0xe844, 16 },
> ++{ 0xe856, 14 },
> ++{ 0xe865, 4295 },
> ++{ 0xf92d, 76 },
> ++{ 0xf97a, 27 },
> ++{ 0xf996, 81 },
> ++{ 0xf9e8, 9 },
> ++{ 0xf9f2, 26 },
> ++{ 0xfa10, 1 },
> ++{ 0xfa12, 1 },
> ++{ 0xfa15, 3 },
> ++{ 0xfa19, 6 },
> ++{ 0xfa22, 1 },
> ++{ 0xfa25, 2 },
> ++{ 0xfa2a, 1030 },
> ++{ 0xfe32, 1 },
> ++{ 0xfe45, 4 },
> ++{ 0xfe53, 1 },
> ++{ 0xfe58, 1 },
> ++{ 0xfe67, 1 },
> ++{ 0xfe6c, 149 },
> ++{ 0xff5f, 129 },
> ++{ 0xffe6, 26 },
> +diff --git a/src/locale/iconv.c b/src/locale/iconv.c
> +index 52178950..4151411d 100644
> +--- a/src/locale/iconv.c
> ++++ b/src/locale/iconv.c
> +@@ -74,6 +74,10 @@ static const unsigned short gb18030[126][190] = {
> + #include "gb18030.h"
> + };
> + 
> ++static const unsigned short gb18030utf[][2] = {
> ++#include "gb18030utf.h"
> ++};
> ++
> + static const unsigned short big5[89][157] = {
> + #include "big5.h"
> + };
> +@@ -224,6 +228,8 @@ static unsigned uni_to_jis(unsigned c)
> + 	}
> + }
> + 
> ++#define countof(a) (sizeof (a) / sizeof *(a))
> ++
> + size_t iconv(iconv_t cd, char **restrict in, size_t *restrict inb, char **restrict out, size_t *restrict outb)
> + {
> + 	size_t x=0;
> +@@ -430,15 +436,24 @@ size_t iconv(iconv_t cd, char **restrict in, size_t *restrict inb, char **restri
> + 				d = *((unsigned char *)*in + 3);
> + 				if (d-'0'>9) goto ilseq;
> + 				c += d-'0';
> +-				c += 128;
> +-				for (d=0; d<=c; ) {
> +-					k = 0;
> +-					for (int i=0; i<126; i++)
> +-						for (int j=0; j<190; j++)
> +-							if (gb18030[i][j]-d <= c-d)
> +-								k++;
> +-					d = c+1;
> +-					c += k;
> ++				/* Starting at 90 30 81 30 (189000), mapping is
> ++				 * linear without gaps, to U+10000 and up. */
> ++				if (c >= 189000) {
> ++					c -= 189000;
> ++					c += 0x10000;
> ++					if (c >= 0x110000) goto ilseq;
> ++					break;
> ++				}
> ++				/* Otherwise we must process an index into set
> ++				 * of characters unmapped by 2-byte table. */
> ++				for (int i=0; ; i++) {
> ++					if (i==countof(gb18030utf))
> ++						goto ilseq;
> ++					if (c<gb18030utf[i][1]) {
> ++						c += gb18030utf[i][0];
> ++						break;
> ++					}
> ++					c -= gb18030utf[i][1];
> + 				}
> + 				break;
> + 			}
> +-- 
> +2.53.0
> +
> diff --git a/package/musl/musl.mk b/package/musl/musl.mk
> index bea9029455..29a9c90ce1 100644
> --- a/package/musl/musl.mk
> +++ b/package/musl/musl.mk
> @@ -26,6 +26,9 @@ MUSL_ADD_TOOLCHAIN_DEPENDENCY = NO
>  
>  MUSL_INSTALL_STAGING = YES
>  
> +# 0003-fix-pathological-slowness-incorrect-mappings-in-icon.patch
> +MUSL_IGNORE_CVES += CVE-2026-6042
> +
>  # musl does not build with LTO, so explicitly disable it
>  # when using a compiler that may have support for LTO
>  ifeq ($(BR2_TOOLCHAIN_GCC_AT_LEAST_4_7),y)
> -- 
> 2.53.0
> 
> _______________________________________________
> buildroot mailing list
> buildroot@buildroot.org
> https://lists.buildroot.org/mailman/listinfo/buildroot
_______________________________________________
buildroot mailing list
buildroot@buildroot.org
https://lists.buildroot.org/mailman/listinfo/buildroot